DNA repair gene XPD Asp312Asn and XRCC4 G-1394T polymorphisms and the risk of autism spectrum disorder.

Autism spectrum disorder (ASD) is a complex disorder, and its extreme heterogeneity further complicates our understanding of its biology. Epidemiological evidence from family and twin studies supports a strong genetic component in ASD etiology. Oxidative stress and abnormal DNA methylation have been implicated in the pathophysiology of ASD. Brain tissues from ASD cases showed higher levels of oxidative stress biomarkers than healthy controls in postmortem analysis. Association between oxidative stress and DNA damage has been well-known. Thus, we sought to investigate a potential link between DNA repair genes and ASD and analyze the role of XPD Asp312Asn and XRCC4 G-1394T gene polymorphisms for ASD in the Turkish population. Genotyping was conducted by PCR-RFLP based on 100 patients and 96 unrelated healthy controls. We, for the first time, demonstrated a positive association between XRCC4 gene variants and ASD risk. Frequencies of XRCC4-1394 T/G+G/G genotypes were higher in patients (%34) than the controls (%18.7). The statistical analysis revealed that the individuals who had XRCC4-1394 T/G+G/G genotype had an increased risk for ASD (OR = 2.23, 95% CI = 1.10-4.55). However, no significant association was found for XPD Asp312Asn polymorphism with the risk of ASD. Our findings suggest that XRCC4 G-1394T polymorphism might be associated with ASD pathogenesis.

Camptodactyly, skeletal changes, ptosis and infertility in a male: a new syndrome?

A 21-year-old male is described with camptodactyly, skeletal changes, ptosis and infertility, which suggests a novel malformation syndrome distinct from other camptodactyly syndromes.

Evaluation of DNA damage using the comet assay in children on long-term benzathine penicillin for secondary prophylaxis of rheumatic fever.

BACKGROUND: Benzathine penicillin is the most widely used antibiotic in the prophylaxis of children with rheumatic fever. The aim of the present study was to evaluate the DNA damage in children receiving one dose of 1.2 million units benzathine penicillin every 4 weeks over a long period to prevent recurrences of rheumatic fever. METHODS: Thirty-five children with confirmed rheumatic fever under benzathine penicillin prophylaxis were enrolled in the study and 35 healthy children with similar ages and socioeconomic backgrounds served as controls. To detect any DNA damage, the comet assay was performed on circulating lymphocytes from the study subjects. RESULTS: Damaged (limited and extensive migration) cells in children on prophylactic therapy were higher than those in controls (P<0.001). CONCLUSIONS: It has been suggested that differences in the comet scores were induced by the administration of benzathine penicillin over a long period of time and further investigations are needed to confirm this toxic effect.

Segregational fidelity of chromosomes in human thyroid tumour cells.

Using fluorescence in situ hybridisation (FISH) we have analysed the segregational fidelity of all the human chromosomes during mitotic cell division. The losses and gains of chromosomes were analysed in human polyploid cell lines derived from a well-differentiated papillary thyroid cancer. These thyroid cells can be cultured for more than 300 population doublings. For the purpose of our study the polyploid nature of the cells may act as a protective buffer against the cell-lethal effects of the loss of individual chromosomes. To evaluate the role of the p53 gene product in maintaining the fidelity of chromosome segregation we compared the frequencies of chromosome loss and gain in cultures with wild-type p53 activity (K1E7neo3) and cultures transfected with plasmids expressing a mutant p53 product (K1E7scx6). Cultures were analysed for the presence of both structurally normal and rearranged chromosomes at both early and late passages. Cell cultures with defective p53 activity showed progressive chromosome loss from a median chromosome number of 87-97 to 75-86. Cell growth in cultures with wild-type p53 activity showed the loss of chromosomes 6, 7, and 8 and the gain of 17 and 20. Cultures expressing mutant p53 activity showed the loss of chromosomes 2, 5, 14 and 17 and the gain of 4 and 22. The combination of defective p53 and growth resulted in further destabilisation with the additional losses of chromosomes 3, 11, 15, 16 and 21. Chromosomes 1, 9, 10, 12, 13, 18, 19, X and Y segregated stably under all the culture conditions as did the structurally rearranged marker chromosomes. The study has demonstrated variation in the fidelity of mitotic chromosome segregation and the influence of p53 gene activity upon the segregation of individual human chromosomes.